Conventionally, a valve device with a fail-safe mechanism is known that is comprised of a valve element; a valve element housing that rotatably accommodates the valve element as well as has a valve element side opening for taking in automotive coolant that has cooled the cylinder head or the like; three communication ports, from first to third, that are connected to a radiator or the like mounted on the valve element housing; and a fail-safe mechanism (see, for example, Patent Document 1).
The fail-safe mechanism of Patent Document 1 includes a thermo-element and an element housing that accommodates the thermo-element. The element housing includes a small-diameter housing for accommodating the thermo-element, a large-diameter housing having an inner diameter of larger diameter than the inner diameter of the small-diameter housing, and a step formed between the small-diameter housing and the large-diameter housing.
A valve element communicating portion that communicates with the valve element housing is provided to the small-diameter housing and a fail safe side opening that opens adjacent to the communication port is provided to the large-diameter housing. The fail safe side opening is closed by a closing member.
The fail-safe mechanism is provided with a valve plate member for closing the step, and a coil spring for biasing the valve plate member to the thermo-element side. An adapter for connecting a line used for connection to the radiator is provided to the third communication port that is connected to the radiator. The adapter is configured separately from the closing member.